Field of the Invention
Embodiments of the present invention generally relate to running casing into a dual gradient well.
Description of the Related Art
Drilling operations that use two different fluid densities or mud weights (Dual Gradient Drilling Systems) have been used to construct subsea wells. See for example, U.S. Pat. Nos. 6,536,540; 6,843,331; and 6,926,101. Benefits of a dual gradient drilling system include reduction of the hydrostatic pressure in the well annulus above the bottom or at a previous casing point while simultaneously maintaining an equivalent hydrostatic pressure at the bottom of the hole as a single gradient fluid system.
One challenge of using a dual gradient system is the process of running in casing. For example, the process of running in casing may cause a pressure surge that may induce fluid losses that would jeopardize the well. Also, the mud weight needed to control pressures in the well must be carefully monitored against the pressure that may induce formation breakdown in the annulus. Formation breakdown may also cause undesired fluid losses to the formation between a casing shoe and total depth.
There is a need, therefore, for systems and methods for running casing in a well with a dual gradient system, which minimize the pressure effects upon the formation.